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<div class="titlepage"><div><div><h4 class="title">
<a name="beast.ref.boost__beast__async_detect_ssl"></a><a class="link" href="boost__beast__async_detect_ssl.html" title="async_detect_ssl">async_detect_ssl</a>
</h4></div></div></div>
<p>
        <a class="indexterm" name="idm44861250486176"></a>
      </p>
<p>
        Detect a TLS/SSL handshake asynchronously on a stream.
      </p>
<h5>
<a name="beast.ref.boost__beast__async_detect_ssl.h0"></a>
        <span class="phrase"><a name="beast.ref.boost__beast__async_detect_ssl.synopsis"></a></span><a class="link" href="boost__beast__async_detect_ssl.html#beast.ref.boost__beast__async_detect_ssl.synopsis">Synopsis</a>
      </h5>
<p>
        Defined in header <code class="literal">&lt;<a href="../../../../../../boost/beast/core/detect_ssl.hpp" target="_top">boost/beast/core/detect_ssl.hpp</a>&gt;</code>
      </p>
<pre class="programlisting"><span class="keyword">template</span><span class="special">&lt;</span>
    <span class="keyword">class</span> <a href="../../../../../../doc/html/boost_asio/reference/AsyncReadStream.html" target="_top"><span class="emphasis"><em>AsyncReadStream</em></span></a><span class="special">,</span>
    <span class="keyword">class</span> <a class="link" href="../concepts/DynamicBuffer.html" title="DynamicBuffer"><span class="emphasis"><em>DynamicBuffer</em></span></a><span class="special">,</span>
    <span class="keyword">class</span> <a href="../../../../../../doc/html/boost_asio/reference/asynchronous_operations.html#boost_asio.reference.asynchronous_operations.completion_tokens_and_handlers" target="_top"><span class="emphasis"><em>CompletionToken</em></span></a> <span class="special">=</span> <span class="identifier">net</span><span class="special">::</span><span class="identifier">default_completion_token_t</span><span class="special">&lt;</span><span class="identifier">beast</span><span class="special">::</span><span class="identifier">executor_type</span><span class="special">&lt;</span><span class="identifier">AsyncReadStream</span><span class="special">&gt;&gt;&gt;</span>
<a href="../../../../../../doc/html/boost_asio/reference/asynchronous_operations.html#boost_asio.reference.asynchronous_operations.automatic_deduction_of_initiating_function_return_type" target="_top"><span class="emphasis"><em>DEDUCED</em></span></a>
<span class="identifier">async_detect_ssl</span><span class="special">(</span>
    <span class="identifier">AsyncReadStream</span><span class="special">&amp;</span> <span class="identifier">stream</span><span class="special">,</span>
    <span class="identifier">DynamicBuffer</span><span class="special">&amp;</span> <span class="identifier">buffer</span><span class="special">,</span>
    <span class="identifier">CompletionToken</span><span class="special">&amp;&amp;</span> <span class="identifier">token</span> <span class="special">=</span> <span class="identifier">net</span><span class="special">::</span><span class="identifier">default_completion_token_t</span><span class="special">&lt;</span> <a class="link" href="boost__beast__executor_type.html" title="executor_type">beast::executor_type</a><span class="special">&lt;</span> <span class="identifier">AsyncReadStream</span> <span class="special">&gt;&gt;{});</span>
</pre>
<h5>
<a name="beast.ref.boost__beast__async_detect_ssl.h1"></a>
        <span class="phrase"><a name="beast.ref.boost__beast__async_detect_ssl.description"></a></span><a class="link" href="boost__beast__async_detect_ssl.html#beast.ref.boost__beast__async_detect_ssl.description">Description</a>
      </h5>
<p>
        This function reads asynchronously from a stream to determine if a client
        handshake message is being received. This call always returns immediately.
        The asynchronous operation will continue until one of the following conditions
        is true:
      </p>
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
            A TLS client opening handshake is detected,
          </li>
<li class="listitem">
            The received data is invalid for a TLS client handshake, or
          </li>
<li class="listitem">
            An error occurs.
          </li>
</ul></div>
<p>
        The algorithm, known as a <span class="emphasis"><em>composed asynchronous operation</em></span>,
        is implemented in terms of calls to the next layer's <code class="computeroutput"><span class="identifier">async_read_some</span></code>
        function. The program must ensure that no other calls to <code class="computeroutput"><span class="identifier">async_read_some</span></code>
        are performed until this operation completes. Bytes read from the stream
        will be stored in the passed dynamic buffer, which may be used to perform
        the TLS handshake if the detector returns true, or be otherwise consumed
        by the caller based on the expected protocol.
      </p>
<h5>
<a name="beast.ref.boost__beast__async_detect_ssl.h2"></a>
        <span class="phrase"><a name="beast.ref.boost__beast__async_detect_ssl.parameters"></a></span><a class="link" href="boost__beast__async_detect_ssl.html#beast.ref.boost__beast__async_detect_ssl.parameters">Parameters</a>
      </h5>
<div class="informaltable"><table class="table">
<colgroup>
<col>
<col>
</colgroup>
<thead><tr>
<th>
                <p>
                  Name
                </p>
              </th>
<th>
                <p>
                  Description
                </p>
              </th>
</tr></thead>
<tbody>
<tr>
<td>
                <p>
                  <code class="computeroutput"><span class="identifier">stream</span></code>
                </p>
              </td>
<td>
                <p>
                  The stream to read from. This type must meet the requirements of
                  <span class="emphasis"><em>AsyncReadStream</em></span>.
                </p>
              </td>
</tr>
<tr>
<td>
                <p>
                  <code class="computeroutput"><span class="identifier">buffer</span></code>
                </p>
              </td>
<td>
                <p>
                  The dynamic buffer to use. This type must meet the requirements
                  of <span class="emphasis"><em>DynamicBuffer</em></span>.
                </p>
              </td>
</tr>
<tr>
<td>
                <p>
                  <code class="computeroutput"><span class="identifier">token</span></code>
                </p>
              </td>
<td>
                <p>
                  The completion token used to determine the method used to provide
                  the result of the asynchronous operation. If this is a completion
                  handler, the implementation takes ownership of the handler by performing
                  a decay-copy, and the equivalent function signature of the handler
                  must be:
                </p>
<pre xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="table-programlisting"><span class="keyword">void</span> <span class="identifier">handler</span><span class="special">(</span>
    <span class="identifier">error_code</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">error</span><span class="special">,</span>    <span class="comment">// Set to the error, if any</span>
    <span class="keyword">bool</span> <span class="identifier">result</span>                 <span class="comment">// The result of the detector</span>
<span class="special">);</span>
</pre>
                <p>
                  Regardless of whether the asynchronous operation completes immediately
                  or not, the handler will not be invoked from within this function.
                  Invocation of the handler will be performed in a manner equivalent
                  to using <code class="computeroutput"><span class="identifier">net</span><span class="special">::</span><span class="identifier">post</span></code>.
                </p>
              </td>
</tr>
</tbody>
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<td align="right"><div class="copyright-footer">Copyright © 2016-2019 Vinnie
      Falco<p>
        Distributed under the Boost Software License, Version 1.0. (See accompanying
        file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
      </p>
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